Troops, backed by heavy artillery and tank fire, blasted suspected hideouts of the Fatah Islam militants inside the Nahr el-Bared camp on the outskirts of the northern port city of Tripoli, as the battle against the militants entered its fifth week, witnesses said.

The intense bombardment sent thick black and white smoke billowing into the air and started fires in several buildings in the camp.

The senior military official, who spoke on condition of anonymity because he was not allowed to make official statements, declined to give details on how the three soldiers were killed. The official also said an undetermined number of soldiers were wounded.

Meanwhile in southern Lebanon, an explosion killed two people at Ein el-Hilweh, Lebanon’s largest Palestinian camp, as members of another Islamic militant group tried to prepare a bomb, Lebanese security officials said.

Three others were wounded in the late afternoon blast, which ripped through a tire shop in the camp.

The fighting at Nahr el-Bared has claimed more than 150 lives — 72 soldiers, at least 60 Fatah Islam militants and more than 20 civilians — since its outbreak on May 20.

— the worst internal violence to engulf Lebanon since the 1975-90 civil war.

In Sunday’s clashes, troops destroyed the militants’ main headquarters located on the edge of the camp, according to the state-run National News Agency.

But the whereabouts of Fatah Islam leader Shaker Youssef al-Absi and his top aides remain unknown.

After inspecting troops deployed around the Nahr el-Bared camp, Lebanese Army Commander Gen. Michel Suleiman said Sunday that the decision to eliminate the Fatah Islam militants was “final and irreversible.”

“There is no other way out for these terrorists except to lay down their arms and surrender to justice before it is too late,” Suleiman said in a statement carried by the NNA.

A senior military official said Sunday there was “no time limit” for the army’s plan to close in on the militants, but would not comment on a report from Lebanon’s leading An-Nahar newspaper that said the military was close to winning the fight.

“The army is taking field measures to put an end to this abnormal situation,” the military official said, speaking on condition of anonymity because he was not authorized to give official statements.

Mediation attempts by Palestinian factions and Islamic clerics to find a peaceful solution to the crisis have so far been unsuccessful.

The Western-backed Lebanese government insists that Fatah Islam militants surrender before the army stops its offensive. However, the group’s leaders have pledged to fight to death.

The fierce combat underscored the tough task Lebanon’s military is facing in its campaign to destroy the militants. But it is difficult to ascertain exactly what is happening inside the besieged camp since journalists have been kept out.

Most of the camp’s 31,000 residents have fled since the fighting began, but the International Committee of the Red Cross has said that between 3,000 and 6,000 civilians remain behind.

Fatah Islam emerged late last year after its leader and some 200 fighters split from the Fatah al-Intifada (Uprising), a pro-Syrian Palestinian faction based in Damascus.

The violence at Nahr el-Bared has threatened to spread to the country’s 11 other Palestinian refugee camps.

Two soldiers were killed in clashes earlier this month with militants at the Ein el-Hilweh camp in southern Lebanon, where the Monday explosion was reported at the tire shop.

The blast occurred as some men were extracting TNT from a 107 mm shell, apparently to use for a bomb, officials said on condition of anonymity because they are not authorized to talk to press.

Otto Warmbier was arrested in January 2016 at the end of a brief tourist visit to North Korea. He had been medically evacuated and was being treated at the University of Cincinnati Medical Center when he died at age 22.